Infrared (IR) remote control devices are commonly used to transmit instructions to receivers in consumer electronics such as televisions, radios, cameras, video cassette recorders, and digital versatile disc (DVD) players. The IR remote control devices use infrared light pulses to transmit instructions to the receiver in accordance with a standard protocol. According to an NEC Corporation standard protocol, when a key of the remote control is pressed and held for a while, a set of pulses indicating a repeat key instruction (i.e., REP_KEY) is sent after a train of pulses that carries coded information for an instruction (i.e., KEY_A) of the key being pressed. The receiver interprets the repeat key instruction REP_KEY by repeating a most recently received non-repeat key instruction. For example, reception of the instruction KEY_A followed by three repeat key instructions REP_KEY will be interpreted as a sequence of four instructions KEY_A.
The above interpretation does not always produce a desired result for both a user and a maker of the consumer electronics. Situations commonly occur where the receiver accepts the instruction key KEY_A, misses a new instruction (i.e., KEY_B) and then receives a subsequent string of repeat key instructions REP_KEY intended for the new instruction KEY_B. As a result, the instruction KEY_A will be repeated because the instruction KEY_A was the most recently accepted instruction. Many factors can cause the new instruction KEY_B to be missed. Such factors include distance from the remote control, an object that shields the remote control from the receiver, and misalignment of the remote control and the receiver.
It is also desirable for a rate of repeating to vary for different keys. For example, a volume instruction and a string of repeat key instructions REP_KEY will be transmitted and received at a fixed rate when the user presses and holds a volume-up key. When the user presses and holds a television channel increment key, a channel increment instruction and another string of repeat key instructions REP_KEY will be transmitted and received at the same fixed rate. However, the manufacturer and the user commonly want the volume to increase at a slow rate for fine control and the television channel to increment quickly for rapid scrolling. With the fixed repeat rate for all repeat key instructions REP_KEY, the volume and channel change at the same rate.
Some remote control keys should not be repeated if pressed and held. In particular, numeric keys used to directly entered a desired television channel must not be repeated to avoid accidental selections of channels 11, 22, 33 and so on. The remote control, though, will transmit the repeat key instruction REP_KEY as long as a numeric key is pressed to comply with the protocol. Experience has shown that it is quite easy for users to cause unwanted repeat key instructions.